Field of the Invention
The present invention relates to a technology for compensating for a change in the luminance of an organic light emitting diode (OLED) panel, and more particularly, to a luminance compensation apparatus of an organic light emitting diode panel, in which a driving chip installed at an outer peripheral portion of an organic light emitting diode panel calculates luminance deviation by using reference pixels installed at an adjacent position, and compensates for luminance for pixel elements aligned in a display area.
Description of the Related Art
An OLED panel is a display panel that electrically excites fluorescent or phosphorescent organic material to emit light, and has been spotlighted as a next generation display panel because it has superior definition and contrast range and can be manufactured in the form of an ultra thin film.
In general, the OLED panel includes a plurality of scan lines, a plurality of data lines, a driving line for transferring a driving voltage, and a plurality of display pixels.
A driving scheme of the OLED panel is largely classified into an analog driving scheme and a digital driving scheme. In the analog driving scheme, a light emitting voltage or a light emitting current supplied to an OLED is adjusted to represent display data. In the digital driving scheme, a time of a light emitting voltage or a light emitting current supplied to an OLED is adjusted to represent display data. In a constant voltage driving scheme, a constant driving voltage is supplied to a driving node of a pixel, and in a constant current driving scheme, a constant driving current is supplied to a driving node of a pixel. In all the constant voltage driving scheme and the constant current driving scheme, luminance of light emitted from an OLED corresponds to display data.
In the constant current driving scheme, since a constant driving current is supplied to the OLED, a light emitting current is almost constant and a change in the luminance of the OLED is small, but there is a problem that luminance is not uniform due to position deviation of a constant current source that supplies the constant driving current. In the constant voltage driving scheme, there is no problem that luminance is not uniform, but even though a constant driving voltage is supplied, since a light emitting current is not constant, a change in the luminance of the OLED is relatively large. For example, when temperature is changed, even though a light emitting voltage is constant, a light emitting current is changed, resulting in a change in the luminance of the OLED.
In addition, due to deviation or experience change of a manufacturing process of the OLED panel, the luminance of the OLED panel has target luminance and deviation. Such luminance deviation degrades the display quality of the OLED panel.
In a conventional OLED panel driving apparatus, luminance is indirectly detected based on a driving current or a threshold voltage of an OLED, and then luminance deviation is calculated and compensated.
When the luminance is indirectly detected as described above, a detection process is complicated and the accuracy is reduced.